Terrible to ride off (4)
I believe the answer is:
dire
'terrible' is the definition.
(synonyms)
'ride off' is the wordplay.
'off' is an anagram indicator.
'ride' anagrammed gives 'DIRE'.
'to' acts as a link.
(Other definitions for dire that I've seen before include "Nearly hopeless" , "Desperate, horrendous" , "Ominous; very bad" , "to speak (13) [FRENCH]" , "Dreadful; grim" .)